You can try putting him in a QT tank with espom salt (1 tsp per gallon) and do daily water changes, Pickle had SBD when I got him, it wasnt as obvious as a bad case but it was the begining (he was a healthy eater to).

If you've tried fasting and epsom salt, then maybe it's an internal tumor.

I would think you would notice any unusual poops from him so that would rule out parasites.

Unfortunately there's nothing you can do about tumors except for make him as comfortable as can be until it's his time. My sister's got one with a tumor on his head that we're doing that for and it's visibly grown.

Has his stomach gotten any bigger since february? If not I'm wondering he's maybe a little deformed.

How long did you do it for?
Even if he seems to get better after 2 days you have to stick with it
I have heard that a lot of betta's have permanent damage to their labrinth organ that makes them have boance issues permantly

LittleBettas is right that even if you see improvement, it's best to continue epsom salt treatments for the full 10 days.

Have you noticed any unusual poops, as Pataflafla asked? My first thought, seeing that he is so big and still eating, is parasites. If he's still eating, it might not hurt to try treating him with Jungle Anti-Parasite Medicated Pellets along with the epsom salt treatments.

he has always had a "bigger then normal" tummy but its rather big atm it seems to vary. I will start another epson salt being that several in the tank seem to have bloated tummys (they fasted last night and are still fat) i cant get medications till monday